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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


3 posters

    RIAA EQ Mod - PAS 2

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    8xlaxx


    Posts : 18
    Join date : 2016-12-10

    RIAA EQ Mod - PAS 2 Empty RIAA EQ Mod - PAS 2

    Post by 8xlaxx Fri Jan 27, 2017 11:41 am

    If anyone has performed the RIAA EQ mod to their PAS2, could you please advise on proper capacitor matching, suggested brands, AND parts numbers if you used a vendor ? (ie. Digi-key,...no affiliation.)
    Thank you!
    j beede
    j beede


    Posts : 473
    Join date : 2011-02-07
    Location : California

    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

    Post by j beede Fri Jan 27, 2017 2:24 pm

    I purchase the majority of my capacitors from Antique Electronic Supply. Excellent inventory, excellent service, no minimum. They sell the usual industrial brands--Sprague, Illinois, Mallory, CE, Solen, and others. Heads up: I discovered that the labeling on some CE types could be damaged/removed by common solvents.

    The caps you will need are inexpensive. Buy more than needed and then "match" values using a simple cap meter. If you intend to use the stock PCB (or clone) you will probably find that many boutique brands take up too much space. I was unable to find every exact value so installed some paralleled sets--one cap on top of the PCB, one below. It worked out well.

    I found that getting rid of that input selector "rat's nest" and the miserable caps located on it was the single best upgrade to the PAS. That preamp now operates without crosstalk--like a "real" preamp.

    RIAA EQ Mod - PAS 2 Verhead
    RIAA EQ Mod - PAS 2 Selector%20switch
    peterh
    peterh


    Posts : 1832
    Join date : 2012-12-25
    Location : gothenburg, sweden

    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

    Post by peterh Fri Jan 27, 2017 5:40 pm

    8xlaxx wrote:If anyone has performed the RIAA EQ mod to their PAS2, could you please advise on proper capacitor matching, suggested brands, AND parts numbers if you used a vendor ? (ie. Digi-key,...no affiliation.)
    Thank you!

    What RIAA mod are you talking about ? is it :
    http://www.curcioaudio.com/Dynaco%20PAS%20RIAA%20EQ%20Correction%20Mod.pdf

    Then read :
    http://www.audioregenesis.com/documents/PAS_Phono.pdf

    and then enjoy your PAS2 "as is"
    avatar
    8xlaxx


    Posts : 18
    Join date : 2016-12-10

    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

    Post by 8xlaxx Fri Jan 27, 2017 11:04 pm

    Thank you Peter. I thoroughly read the article. The screwdriver is staying put on the bench. Will just have to sacrifice the Tape Out low-end frequency compromise/response.

    Again, appreciate the link.
    j beede
    j beede


    Posts : 473
    Join date : 2011-02-07
    Location : California

    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

    Post by j beede Sat Jan 28, 2017 3:39 pm

    Regardless of what you do regarding the RIAA circuit... by all means replace your input selector and its associated wiring. If you are still running the stock power supply--that needs to go too.

    Replacing the input selector is an ideal time to replace the stock RCA I/O board. This is not a trivial job but makes the PAS perform like a much more modern preamp.
    peterh
    peterh


    Posts : 1832
    Join date : 2012-12-25
    Location : gothenburg, sweden

    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

    Post by peterh Sat Jan 28, 2017 4:30 pm

    j beede wrote:Regardless of what you do regarding the RIAA circuit... by all means replace your input selector and its associated wiring. If you are still running the stock power supply--that needs to go too.

    Replacing the input selector is an ideal time to replace the stock RCA I/O board. This is not a trivial job but makes the PAS perform like a much more modern preamp.
    Why replace the input selector ? Motivate please.

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    RIAA EQ Mod - PAS 2 Empty Re: RIAA EQ Mod - PAS 2

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